Humans INTUITIVELY avoid others who carry disease, even before they become conscious of symptoms

The next time your instincts tell you to avoid someone, it may just be your brain protecting your system from contagious diseases. A new study has found that the human brain can detect diseases in other people even before symptoms manifest, ScienceDaily.com reported. The study, published in Proceedings of the National Academy of Sciences (PNAS), found that the human brain is better at reading signals and discovering early-stage diseases than scientists previously thought. More than that, the study also found that humans act on the information, showing less preference for people infected with disease.

In carrying out the research, the scientists focused on two groups of participants. They activated the immune response in the first group of participants, injecting them with harmless sections of bacteria. They then developed symptoms of disease, such has tiredness, pain, and fever. The symptoms only lasted for a few hours, during which time photos, videos, and smell samples were recorded from the participants.

The smells, images, and videos were then shown to the second group of participants, along with samples and recordings from healthy people without symptoms. The second group of participants were asked to rate how much they liked the people, as an MR scanner tracked their brain activity. Afterwards, the second group of participants were asked to identify based solely on the photographs which of the people looked sick, which they thought were attractive, and which they would want to socialize with.

The results showed that there was a remarkable difference in the way people respond to healthy people compared to sick people, with participants showing a preference for healthy people.

“The study shows us that the human brain is actually very good at discovering this and that this discovery motivates avoidance behavior,” lead investigator Mats Olsson, professor at Karolinska Institutet’s Department of Clinical Neuroscience.

“Common sense tells us that there should be a basic behavioural repertoire that assists the immune system. Avoidance, however, does not necessarily apply if you have a close relationship with the person who is ill,” Olsson explained. “For instance, there are few people other than your children who you’d kiss when they have a runny nose. In other words, a disease signal can enhance caring behavior in close relationships. With this study, we demonstrate that the brain is more sensitive to those signals than we once thought.”

There are many ways that the brain protects the rest of the body from being physically compromised. Apart from alerting the body to potential threats (i.e people carrying diseases), the brain can also impact how the body recovers once a disease is already contracted. There are studies that show that the simple act of positive thinking can help speed up recovery from surgery and even manage serious diseases such as cancer, heart disease, and AIDS, PsychCentral.com said.

Scientists suspect that the healing powers of positive thinking go back to the strong connection between the mind and the immune system. For instance, one study showed that first year law students who expressed optimism at the start of the school year were found to have better-functioning immune system cells than the students who were worried. Conversely, pessimism can trigger the release of stress hormones in the bloodstream.

Evidently, the power of the brain over the rest of the body is unparalleled, with new discoveries of its effects on the body coming up every day.